In the fabrication of semiconductor devices, increased density and speed has caused a shift in the metallization system from aluminum (Al) to copper (Cu) to reduce the resistance of the conductor. To reduce the capacitive coupling between adjacent metal lines, materials having low k dielectric constant are used to form dielectric layers between adjacent metal lines. Furthermore, to prevent diffusion of copper containing materials into the surrounding low k dielectric layers, diffusion barrier layers are incorporated between metal layers and dielectric layers.
However, due to reliability issues of electromigration resistance and void formation, adhesion between copper and the diffusion barrier layer is a major concern. With typical copper diffusion barrier layers now available, copper has less than desirable adhesion to the barrier layers and has a tendency to agglomerate for future technology nodes such as 22 nm and beyond future size.
U.S. Pat. No. 6,271,131 discloses a method of forming a rhodium (Rh) containing layer such as platinum-rhodium (Pt—Rh) alloy as diffusion barrier via chemical vapor deposition. However Pt and Rh are very expensive noble metals which makes it impossible to adopt in the semi-conductor industries.
U.S. Pat. No. 1,063,687 describes a titanium-tantalum (Ti—Ta) barrier layer film for use in conjunction with an interconnect film such as Cu. The Ti rich/Ta deficient portion provides good adhesion to the dielectric film and the Ta rich/Ti deficient portion forms a hetero-epitaxial interface with the interconnect film and suppresses the formation of inter-metallic compounds.
U.S. Pat. No. 5,942,799 discloses a multilayer diffusion barrier comprising a refractory metal such as tungsten (W), titanium (Ti), tantalum (Ta), molybdenum (Mo); and a
refractory metal nitride such as WNx, TiN, TaN; and a second sublayer formed from a refractory metal nitride, a refractory metal silicon nitride such as TiSixNy, TaSixNy, WSixNy.
US 20050070097 discloses a very thin multilayer diffusion barrier for a semiconductor device and fabrication method thereof. The multilayer diffusion barrier is fabricated by forming a very thin, multilayer diffusion barrier composed of even thinner sub-layers, where the sub-layers are only a few atoms thick.
US 2006001306 reveals a method to enhance thermal stability and reliability by forming a hybrid type nanocomposite diffusion barrier deposited by atomic layer deposition using precursors composing of a Ti precursor and a Ta precursor.
US 2006115476 covers the ruthenium alloy as copper diffusion barrier comprising of ruthenium and at least one element from groups IV, V, or VI of the Periodic Table or a combination thereof.
US20070264816A1 discloses a method for forming a metal interconnect to use a Cu—Al alloy layer on the barrier layer. The Cu—Al alloy layer may be formed by sequential ALD or CVD deposition of an aluminum layer and a copper layer followed by an annealing process. Alternately, the Cu—Al alloy layer may be formed in-situ by co-pulsing the aluminum and copper precursors.
US 20070123043 describes a tin and nickel-containing copper alloy as diffusion barrier in a copper interconnect. The tin and nickel-containing copper alloy may be formed in a gaseous ambient on the basis of tin hydride and nickel, carbon monoxide in a thermally driven reaction.
Maury, F. and F. Ossola (1992). “Evaluation of Tetra-Alkylchromium Precursors for Organometallic Chemical Vapor-Deposition. 2. Unusual Low-Temperature Chromium Carbide Deposition from Cr[C(CH3)3]4.” Thin Solid Films 219 (1-2): 24-29
Ossola, F. and F. Maury (1997). “MOCVD route to chromium carbonitride thin films using Cr(NEt2)(4) as single-source precursor: Growth and mechanism.” Chemical Vapor Deposition 3(3): 137-143.
Accordingly, there remains a need for an improved adhesion process, or metallization process, which controls the agglomeration of copper, and improves the adhesion between barrier layers and subsequently deposited metal layers. There is also a need for an adhesion-promoting materials, or glue layer materials, which promote adhesion between barrier layers and subsequently deposited metal layers.